Engine Diseled this weekend once

[hostage]

Hello,

I was riding around in my boat and after pulling someone around in the tube for a few minutes the engine started to disel. This is the first time it has done this, this season when I turned the ignition off. Could this be caused from me turning the engine off to quickly after pulling someone in a tube? It did it once that day and no more before or after.

Regards,

-Hostage

 

[Don S]

Re: Engine Diseled this weekend once

Could this be caused from me turning the engine off to quickly after pulling someone in a tube?

Absolutely.

 

[hostage]

Re: Engine Diseled this weekend once

Don - Thank you, I will wait a little longer before turning off the engine.

 

[Jlawsen]

Re: Engine Diseled this weekend once

Don - Thank you, I will wait a little longer before turning off the engine.

There's a couple of basic causes for run-on. The most common is carbon buildup on the piston tops. In that situation, if you get it hot the carbon acts like a glo plug. It can also be brought on by too much intial timing that creates a lean condition. That's the most dangerous one because if you idle a lot you can melt a piston down. Winterizing can cause an intial carbon build up that generally burns off and can cause run-on the first time out. Sounds to me like that's what happened to you. If it happens again, get the timing checked and you might want to make sure it's idleing at the right RPM. If the idle is either too high or too low then a carb cleaning might be in order because it could be the source of a lean condition.

As a side note, engine coolant temps may or may not indicate a problem. They usually do but I've seen pistons go and the owners would tell me it didn't get hot (hard to read the truth in that) but you can't very well call your customer a liar..LOL..

 

[Don S]

Re: Engine Diseled this weekend once

The most common is carbon buildup on the piston tops.

That might be true on cars, but not so much on boats. Boats seldom build up all that carbon.
On boats, the two biggest problems are not allowing a cool down for a minute or so after a hard run, or idle rpm set too high. Especially on the 3.0 and 4.3L engines.

 

[Jlawsen]

Re: Engine Diseled this weekend once

That might be true on cars, but not so much on boats. Boats seldom build up all that carbon.
On boats, the two biggest problems are not allowing a cool down for a minute or so after a hard run, or idle rpm set too high. Especially on the 3.0 and 4.3L engines.

Don, if an engine runs on it's got a problem and it doesn't matter if its in a car or a boat. If the tops of the pistons are hot enough to continue igniting fuel after the normal ignition source has been removed something is not right. I don't care if you've been tubing or not the piston tops won't normally get that hot unless you have a lean condition. Even carboned up pistons should never get that hot.

All we know is that the OP was tubing and it only happened once that day. For all we know it could have been a cooling issue that needs to be looked into. I'm not saying you need to tear a motor down everytime it acts a little weird but you should take the time to look into it at the next opportunity. Replacing motors isn't cheap and might be avoided if the right advice is taken.

 

[FreeBeeTony]

Re: Engine Diseled this weekend once

Don, if an engine runs on it's got a problem and it doesn't matter if its in a car or a boat. If the tops of the pistons are hot enough to continue igniting fuel after the normal ignition source has been removed something is not right. I don't care if you've been tubing or not the piston tops won't normally get that hot unless you have a lean condition. Even carboned up pistons should never get that hot.

All we know is that the OP was tubing and it only happened once that day. For all we know it could have been a cooling issue that needs to be looked into. I'm not saying you need to tear a motor down everytime it acts a little weird but you should take the time to look into it at the next opportunity. Replacing motors isn't cheap and might be avoided if the right advice is taken.

Oh Boy.............be careful.

 

[Scott Danforth]

Re: Engine Diseled this weekend once

or shut the motor off in gear. that will snub it and prevent dieseling. I was able to get any of my boats to diesel by a hard day of watersports, especially when trying to pull up new skiers.

 

[hostage]

Re: Engine Diseled this weekend once

I have been out a few times this year and haven't had diseling until today. Last year I did have some diseling, though I think it quit after i had the rotor replaced by mechanic. I also replaced the spark plugs at the end of the year. I have heard it caugh and sputter a little bit when starting it, though that was until I found out I was starting it wrong.

I don't really do many water sports (friends are wimps), though I was pulling a couple of friends around the other day and the last run of the day the tuber signaled stop so I put it in neutral and then I turned off the ignition. I normally never kill it that quick and that is why I asked.